How did the cosmonauts react? It is possible to make inferences from the analyses performed by the medics, the state of the cabin, and the data recorded by the 'black box'. During the descent, each cosmonaut wore a medical belt with various sensors and the data on their vital functions was recorded. Prior to their return, the general physical state of each man was good. Dobrovolskiy's pulse in a normal, unstressed state was 7885 beats per minute. Volkov, being more dynamic and emotional, was usually higher, and at the time of undocking from Salyut his pulse increased to 120, perhaps reflecting his concern about the hatch seal. Patsayev's pulse was between 92 and 106.
During the first second after the separation of the spacecraft's modules the pulses of all three men dramatically increased. Dobrovolskiy rose to 114. Volkov shot up to 180! Four seconds after the onset of depressurisation Dobrovolskiy's respiration rate was 48 breaths per minute; the normal rate is 16. Such rates are characteristic of a sudden oxygen starvation. The rapid increases in pulse and respiration indicate that the crewmembers were immediately aware of what was occurring. In addition to hearing the air leaking out and feeling the pressure fall, they would have heard a loud siren and seen the value of the cabin pressure decline on the indicator set in the lower left corner of the main instrument panel. There would also have been physical indications, including a rapid fall in temperature and air fogging as the water vapour condensed. They would have suffered the effects of decompression - an immediate strong pain in the head, chest and abdomen, followed by burst eardrums and blood streaming from the nose and ears. Their heart rates rose during the first 20 seconds, but by 60 seconds had reduced to just 40 per cent of the baseline.
Death was not instantaneous. Due to out-gassing of oxygen from the venous blood supply to the lungs, the men would have remained consciousness for 50-60 seconds. However, they could have moved about and tried to remedy their plight only during the first 13 seconds; this being the 'time of useful consciousness', corresponding to the time that it took for the oxygen-deprived blood to pass from the lungs to the brain. Because the valves were situated above their couches, Dobrovolskiy and Patsayev attempted to take action. Being in the centre, nearest the hatch, Dobrovolskiy was in the best position to act. However, the cosmonauts did not know the actual source of the leak. Recalling the difficulty that they had faced in sealing the hatch, their initial diagnosis must have been that the air was leaking through the hatch. Dobrovolskiy unbuckled and pulled himself to the hatch. However, it was properly closed. When Volkov and Patsayev switched off the radio equipment in order to listen to the hiss in an effort to identify the source of the leak, this was realised to be one of the two valves. But which one? Valve No. 2, above Patsayev, was marked as 'open', so he went to try to close it. But it was No. 1 which was open. It is difficult to know who did so, but either Patsayev or Dobrovolskiy began to close the hand-operated shutter of valve No. 1. However, in normal circumstances it required at least 35 seconds to close the valve by hand, and by the time they passed out it was only partially cycled. Volkov was too far away from the valves to assist, so he remained strapped into his couch. By virtue of being more active, Dobrovolskiy and Patsayev would probably have lost consciousness before Volkov, for whom the frustration of being unable to assist must have been intense.
They died rapidly. The initial paralysis due to oxygen starvation would have been followed by general convulsions. During this time, water vapour rapidly formed in the venous blood, and in soft tissue. Blood and other bodily fluids boiled and turned to vapour, causing the body to swell to perhaps twice its normal volume. The heart rate initially soared, but then diminished to an unsustainable rate. The arterial blood pressure dropped to zero after about 60 seconds, but the venous pressure rose due to gas and vapour distending the venous system. Within a minute, the venous pressure exceeded the arterial pressure. In effect, there was no circulation of blood. After the initial rush of gas from the lungs during decompression, gas and vapour continued to flow out through the airways, and the sustained evaporation of water chilled the mouth and nose to almost freezing temperatures. The remainder of the body would have cooled more slowly. The first fatal damage occurred in the cosmonauts' lungs, as the most vulnerable part of the body in such circumstances. They naturally tried to hold their breath, but as the cabin pressure declined the lungs and thorax became over-extended, tearing and rupturing the lung tissue and capillaries. The trapped air was forced directly into the blood, following the ruptured blood vessels and creating massive air bubbles in the vital organs, including the heart and brain. Clinical death began after 90-100 seconds, simultaneously in all three men. By 110 seconds after the separation of the modules there were no heart or respiration rates recorded. Ten seconds later, life was extinct. The cabin remained in vacuum for 11.5 minutes, then began to fill with air from the upper atmosphere.
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